CuInSe.sub.2 is a member of the I-III-VI.sub.2 class of chalcopyrite compounds (Groups I, III and VI of Mendelyeev's Periodic Table). B. Tell et al. in Journal of Applied Physics 43, 2469 (1972) disclose that CuInSe.sub.2 crystals having p- and n-type conductivity can be obtained by heat treatment under maximum and minimum Se atmosphere. P. Migliorato et al. in Applied Physics Letters 24, 434 (1974) describe the fabrication of a homojunction electroluminescent device by diffusing Se into n-type CuInSe.sub.2 crystals. S. Wagner et al. in Applied Physics Letters 25, 434 (1974) describe the fabrication of a CuInSe.sub.2 /CdS p-n heterojunction photovoltaic detector.
The technique of forming p-n junctions by ion implantation has been known for a number of years. In general, the techniques has been investigated with respect to p-n junction formation in common semiconductor materials, such as silicon, germanium, gallium arsenide, gallium antimonide, indium arsenide, and the like. While the diffusion method, as mentioned above, has been employed to create a p-n junction in CuInSe.sub.2, it would be particularly desirable to provide an ion implantation method for forming the junction. This is the case since several advantages accrue from the utilization of the ion implantation method as compared to the diffusion method. Thus, ion implantation makes it possible to achieve uniform and controlled doping as well as controlled junction depth and profile. Furthermore, the low temperature processing involved in the ion implantation method is a definite advantage over the high temperature requirements of the diffusion method.
It is an object of this invention to provide an ion implantation method for preparing p-n junctions in p-type CuInSe.sub.2 crystals.
Another object of the invention is to provide a method for fabricating p-n junction light emitters and photovoltaic detectors by the ion implantation of certain dopants into p-type CuInSe.sub.2 crystals.
A further object of the invention is to provide a method for fabricating diodes having a p-i-n structure.